Well, this is a tricky question. But if you have played any other version then you may know that a step count an EXP. Point for your Pokemon in Day-Care.
I Didn't clearly got your question though. You said ''Pressing B into walls'' Day-care only counts your steps, not your clicks. Even if you press B a thousand of times on the wall, it won't do a thing. Just try to take as many steps as you can and then see your Pokemon grow.